Repairable labyrinth seal

ABSTRACT

A repairable labyrinth seal of a gas turbine engine comprises at least one fin having a base with a thickness and a tip portion extending therefrom. A shoulder distinguishes the base from the tip portion. The shoulder defines a machining site suitable for receiving a welded replacement piece for shaping a new tapered tip portion following removal of a worn tapered tip portion.

TECHNICAL FIELD

The invention relates generally to a gas turbine engine and, moreparticularly, to a repairable labyrinth seal.

BACKGROUND OF THE ART

Labyrinth seals of a gas turbine engine are often used as air-oil sealsto provide sealing of rotating shafts of bearing compartments and gearcases, etc. Labyrinth seals typically comprise knife edges or teeth orfins which rotate relative to a surrounding seal land or runner, theknife edges having tight tip clearances with a surface of the land orrunner. The relative rotation between the knife edges and the runner oflabyrinth seals, however, can tend to cause knife edge wear which cansignificantly reduce the sealing capability.

Labyrinth seals are life limited parts that are not repairable and aretherefore generally not attached to high cost parts such as impellers orrotors. Instead they are components in and of themselves. Separatelabyrinth seals require additional part count per engine, and additionalcost due to extra machining of mating parts.

Accordingly, there is a need to provide a repairable labyrinth seal thataddresses at least some of the above issues.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a repairablelabyrinth seal.

In one aspect, the present invention provides a repairable labyrinthseal comprising at least one fin, the fin having a base with a thicknessand a tapered tip portion extending therefrom, at least one shoulderdistinguishing the base from the tapered tip portion, the shoulderdefining a machining site suitable for receiving a welded replacementpiece for shaping a new tapered tip portion following removal of a worntapered tip portion.

In a second aspect, the present invention provides a rotor assembly of agas turbine engine comprising a rotary component having at least oneintegral labyrinth seal having at least one fin and a runner mounted forrelative rotation, the runner having a runner surface facing the fin,the fin having a base with a thickness and a tapered tip portionextending therefrom, at least one shoulder distinguishing the base fromthe tapered tip portion, the shoulder defining a machining site suitablefor receiving a replacement piece for shaping a new tapered tip portionfollowing removal of a worn tapered tip portion.

In a third aspect, the present invention provides a method of repairinga labyrinth seal having at least one worn fin comprising removing a worntip portion of the fin down to a surface sufficient for receiving aweld, and welding a replacement piece to said surface.

In a fourth aspect, the present invention provides a repairablelabyrinth seal comprising at least one fin extending outwardly from aseal body, the fin having a base portion having a height relative tosaid seal body and a predetermined transversal thickness, a tip portiontapering from said base portion away from said seal body, a referenceplane separating the base portion from the tip portion defining amachining site, the predetermined thickness of the base portion at themachining site allowing for machine removal of the tapered tip portionand replacement of a new tapered tip portion to the base at themachining site.

Further details of these and other aspects of the present invention willbe apparent from the detailed description and figures included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures depicting aspects ofthe present invention, in which:

FIG. 1 is a cross-sectional view of a gas turbine engine;

FIG. 2 is a cross-sectional view of a compressor section of the engineof FIG. 1, showing a repairable labyrinth seal in accordance with aparticular embodiment of the present invention;

FIG. 3 is a cross-sectional view of a labyrinth seal in accordance withthe prior art; and

FIG. 4 is a cross-sectional view of the repairable labyrinth seal shownin FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a gas turbine engine 10 of a type preferably providedfor use in subsonic flight, generally comprising in serial flowcommunication a fan 12 through which ambient air is propelled, amultistage compressor 14 for pressurizing the air, a combustor 16 inwhich the compressed air is mixed with fuel and ignited for generatingan annular stream of hot combustion gases, and a turbine section 18 forextracting energy from the combustion gases.

FIG. 2 illustrates a section of the compressor 14 including aconventional non repairable labyrinth seal 20 and a repairable labyrinthseal 22. Particularly, the non repairable labyrinth seal 20 isexemplified mounted concentrically about a rotating shaft 24 providingsealing between the rotating shaft 24 and a surrounding part 28. Therepairable labyrinth seal 22 is shown integrally formed oil impeller 30providing sealing between impeller 30 and a portion of the stationaryouter casing 32 defining the gas path.

FIG. 3 depicts an enlarged view of the non-repairable labyrinth seal 20,whish has a configuration commonly known in the art. Particularly,labyrinth seal 20 can generally be described as comprising a pluralityof fins 34 which rotate with the rotating shaft 24 relative to ajuxtaposed runner 36. Tips 38 of the fins 34 are disposed adjacent torunner surface 40 of runner 36 in very tight clearance thereto such thata substructure fluid seal is provided therebetween. Fins 34 extend froma base element 42, tapering all the way to the tips 38.

FIG. 4 depicts an enlarged view of repairable labyrinth seal 22 inaccordance with a particular embodiment of the present invention.Labyrinth seal 22 also comprises a plurality of fins 44 which rotatewith the impeller 30 relative to juxtaposed runner 46. Tips 48 of thefins 44 are disposed adjacent to the runner surface 50 of the runner 46in very tight clearance thereto such that a substructure fluid seal isprovided therebetween. Fins 44 extend integrally from the impellersurface.

Still referring to FIG. 4, it can be seen that the fins 44 have aparticular shape differing from that of fins 34 of generic labyrinthseal 20. Fins 44 comprise a base 52 and a tapered tip portion 54extending therefrom. Particularly, the base 52 has a generallyrectangular shape with a predetermined thickness t and a height h.According to one embodiment, t=0.040 inch and h=0.060 inch. Thethickness t may range from about 0.030 inch to about 0.060 inch. Theheight h may range from about 0.030 inch to about 0.200 inch. Notably,the base 52 has a height h that is generally greater than half theoverall fin height.

A shoulder 56 is defined on each side of the base 52 at height hdistinguishing between the two sections of the fin 44. Shoulders 56 eachdefine an edge 57 leading into the tapered tip portion 54. An imaginaryreference plane P located at height h separating the base 52 from thetapering tip portion 54 defines a machining site 58 on the base 52. Thereference plane P is generally parallel to an axis of rotation of thegas turbine engine 10. The machining site 58 is identified by shoulders56 and is suitable for receiving a welded replacement piece shaped intoa new tapered tip portion following removal of a worn tapered tipportion. Notably, the height of the new tapered tip portion isdetermined from the reference plane P.

The predetermined thickness t of the base 52 at the machining site 58allows for removal of a worn tapering tip portion, preferably bymachining off the entire worn tapered tip portion down to the base 52.The predetermined thickness t at the machining site 58 also allows forreplacement of a new piece of material for shaping a new tapering tipportion welded to the base 52 at the machining site 58. Thus, the fins44 have a particular shape propitiously suited for subsequent reparationby way of machining. The minimum surface area of each fin machiningsite, i.e. the cross-section area of base 52, is at least equal to about0.25 inch² to permit welding.

A method of repairing a labyrinth seal in accordance with a particularembodiment of the present invention is described below. The first stepentails a skilled person to identify shoulder 56, and more specificallythe reference plane P as the machining site 58. The next step is tomachine off the worn tapered tip portion down to the machining site 58,and then to subsequently weld on a replacement piece of material forshaping a new tapered tip portion. Preferably, the replacement piece ofmaterial is provided as a ring and a butt weld is used to attach thereplacement piece at the machining site 58. Then, the welded replacementpiece is heat treated and inspected for quality control. Finally, thereplacement piece of material is machined into the final shape of a newtapered tip portion.

Thus, the repairable labyrinth seals of the present inventionexemplified in the above description and in the accompanying Figuresprovided many advantages over generic labyrinth seals. One advantage isthat repairable labyrinth seals can be made integral with high cost andcomplex components such as impellers and rotors, as described above,which advantageously reduces overall engine part count. Anotheradvantage of using an integral labyrinth seal design is that thefunctionality of the seal is improved due to the fact that theeccentricity of the repairable labyrinth seal diameter can be machinedrelative to the rotor datums. Thus, a repairable labyrinth seal designenables part integration thereby improving sealing performance.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without department from the scope of the invention disclosed.For example, in this particular embodiment the fins 44 of repairablelabyrinth seal 22 are disposed on a component which rotates within astationary surrounding runner, but it is to be understood that theconverse is also possible, namely that the runner surface rotates andthe fins of the labyrinth seal disposed in close juxtaposition theretoremain stationary. Further, both portions of the labyrinth seal, ie. thefins and the runner, may be rotating.

Still other modifications which fall within the scope of the presentinvention will be apparent to those skilled in the art, in light of areview of this disclosure, and such modifications are intended to fallwithin the appended claims.

1. A repairable labyrinth seal comprising at least one fin, the finhaving a base with a thickness and a tapered tip portion extendingtherefrom, at least one shoulder distinguishing the base from thetapered tip portion, the shoulder defining a machining site suitable forreceiving a welded replacement piece for shaping a new tapered tipportion following removal of a worn tapered tip portion.
 2. Therepairable labyrinth seal as defined in claim 1, wherein the shoulderdefines an edge.
 3. The repairable labyrinth seal as defined in claim 2,wherein the edge leads into the tapered tip portion.
 4. The repairablelabyrinth seal as defined in claim 3, wherein the fin has a pair ofopposed shoulders defining edges.
 5. The repairable labyrinth seal asdefined in claim 1, wherein the machining site defines a reference planefor shaping a new tapered tip portion.
 6. The repairable labyrinth sealas defined in claim 4, wherein the reference plane is generally parallelto an axis of rotation of the gas turbine engine.
 7. The repairablelabyrinth seal as defined in claim 6, wherein a height of the newtapered tip portion is determined from the reference plane.
 8. Therepairable labyrinth seal as defined in claim 1, wherein the base has across-sectional area predetermined to allow for the machining site toreceive a weld thereon.
 9. The repairable labyrinth seal as defined inclaim 1, wherein the fin has an overall height and the base has a heightthat is greater than half the overall fin height.
 10. A rotor assemblyof a gas turbine engine comprising a rotary component having at leastone integral labyrinth seal having at least one fin and a runner mountedfor relative rotation, the runner having a runner surface facing thefin, the fin having a base with a thickness and a tapered tip portionextending therefrom, at least one shoulder distinguishing the base fromthe tapered tip portion, the shoulder defining a machining site suitablefor receiving a replacement piece for shaping a new tapered tip portionfollowing removal of a worn tapered tip portion.
 11. The motor assemblyas defined in claim 10, wherein the shoulder defines an edge.
 12. Therotor assembly as defined in claim 11, wherein the edge leads into thetapered tip portion.
 13. The rotor assembly as defined in claim 12,wherein the fin has a pair of opposed shoulders defining edges.
 14. Therotor assembly as defined in claim 10, wherein the machining sitedefines a reference plane for shaping a new tapered tip portion.
 15. Therotor assembly as defined in claim 14, wherein the reference plane isgenerally parallel to an axis of rotation of the gas turbine engine. 16.The rotor assembly as defined in claim 15, wherein a height of the newtapered tip portion is determined from the reference plane.
 17. Therotor assembly as defined in claim 10, wherein the thickness of the baseis predetermined to allow for the machining site to receive a weldthereon.
 18. The rotor assembly as defined in claim 10, wherein the finhas an overall height and the base has a height that is greater thanhalf the overall fin height.
 19. The rotor assembly as defined in claim10, wherein the rotary component is an impeller.
 20. A method ofrepairing a labyrinth seal having at least one worn fin comprisingremoving a worn tip portion of the fin down to a surface sufficient forreceiving a weld, and welding a replacement piece to said surface. 21.The method of claim 20 comprising: identifying a shoulder distinguishingbetween a base and a worn tip portion of the fin, and wherein theremoving step comprises machining off the worn tip portion down to theshoulder, the surface receiving the weld being defined at said shoulder.22. The method as defined in claim 20, further comprising the step ofheat treating the welded piece.
 23. The method as defined in claim 22,further comprising the step of inspecting the welded piece.
 24. Themethod as defined in claim 23, further comprising the step of shapingthe welded piece into a replacement tapered tip portion.
 25. Arepairable labyrinth seal comprising at least one fin extendingoutwardly from a seal body, the fin having a base portion having aheight relative to said seal body and a predetermined transversalthickness, a tip portion tapering from said base portion away from saidseal body, a reference plane separating the base portion from the tipportion defining a machining site, the predetermined thickness of thebase portion at the machining site allowing for machine removal of thetapered tip portion and replacement of a new tapered tip portion to thebase at the machining site.